1. Field of the Invention
The present invention relates to damping apparatus. In particular, the present invention relates to damping apparatus as in the deployment mechanisms of spacecraft.
While the present invention is described herein with reference to a particular embodiment or illustration, it is understood that the invention is not limited thereto. Those of ordinary skill in the art, having access to the teachings provided herein, will recognize additional modifications, applications and embodiments within the scope of the invention.
2. Description of the Related Art
As is well known, conventional rotary damping mechanisms employ a paddle mounted on a shaft for movement within a chamber filled with a damping fluid. As the shaft is rotated within the housing the fluid flows from one side of the paddle to the other through a small gap between the paddle and the housing. This action provides a damping force proportional to velocity and hence the rate of deployment can be limited.
A damping and deployment mechanism is typically a damping mechanism fitted with an actuator, typically a spring, and a latch. Thus, the spring provides the actuation force which is damped by the damping mechanism. The damping and deployment mechanism will experience a controlled motion to the end of travel at which time the latches will engage and hold the mechanism in its deployed position.
Unfortunately, these mechanisms typically have several shortcomings of which the leakage of damping fluid is but one example. In many applications, leakage of damping fluid may be tolerated; however, in certain more demanding applications, this leakage may be problematic. For example, in space and other remote environments, leakage of fluid from a damping mechanism in a deployment system may cause enough damage to impact on the success or failure of the mission. That is, the leakage may reduce the damping capacity of the mechanism and allow a substantial force to be applied to the spacecraft structure, due to increased impact velocities, causing breakage of and damage to critical system components. This may also lead to contamination of adjacent spacecraft components. Thus, durable, reliable operation of such damping and deployment mechanisms is often a design objective of high priority as maintenance, repair, and replacement may be quite costly or impossible.
Another typical shortcoming of conventional damping and deployment mechanisms is that the mechanism is typically constrained to latch in a fixed position. In some applications, there is a need to latch, albeit temporarily, in some intermediate position. Thus, variable latching, the capability to latch in any position within the range of movement of the deployment arm, is deemed to be desirable.
Further, there is typically no provision for varying the rate of deployment of structures using conventional deployment mechanisms. It is considered to be desirable that the rate and degree of deployment be controlled. This would permit the use of more powerful actuators (heavier springs) and still control the deployment rate.
Also, conventional damping mechanisms do not add to the stiffness of the deployed systems. That is, once the deployment is complete, only a latch prevents the joint from becoming fluid again. It would be advantageous to provide a stronger joint than is typically characteristic in a simple latch.
Further, conventional systems are gap dependent. That is, the damping rate is typically a function of the gap between the paddle and the walls of the chamber through which the fluid must flow. The need to control the dimensions of these gaps adds significantly to the cost of manufacture of conventional deployment mechanisms.
There is, therefore, a need in the art for a simple, low cost improved damping and deployment mechanism that is less likely to leak; offers variable latching; is rate controllable; is load independent; and adds to the stiffness of the deployed system.